Location system

ABSTRACT

Systems and methods for allowing the location of transmitter to be determined (approximated) without requiring its distance from a receiver to be precisely known. Methods for determining a location of a transmitter without precise distance calculations. In one embodiment, a method is disclosed having the steps of: for a receiver, estimate a first zone a first transmitter is in; for remaining receivers that can receive a given transmitter, each estimate a second zone a first transmitter is in; and determine if there are overlaps in any of the zones. In another embodiment a potential target area is defined wherein the location of a transmitter can estimated.

REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to U.S. Provisional PatentApplication Ser. No. 60/512,897, filed Oct. 20, 2003, entitled LocationSystem, the content of which is herein incorporated by reference.

TECHNICAL FIELD

The present invention relates to determining a location of one or moreobjects.

BACKGROUND

It is useful to know the location of people or objects for severalreasons. The location in-and-of itself is important because it allowsanother party to find something that is lost, such as a child or a pieceof expensive equipment. Location can also be valuable as a piece of dataused in conjunction with other information. For example, knowledge aboutthe location of a portable laptop computer combined with knowledge aboutthe location of all the printers in a building allows a system toautomatically route a print job from the laptop to the nearest printer,thus saving time and aggravation. The knowledge of who is in aparticular room allows a system to adjust the temperature or lighting ofthat room to the individual's preferences or route that person'stelephone calls to the phone in that room. These applications arepresented here as examples illustrating the utility of a system thatallows the location of a person or object to be known.

Existing systems are generally based on one of two principles. In thefirst method they measure the amount of time it takes a signal to travelfrom point A to point B then calculate the distance between the twopoints. Given three different distance calculations, a precise locationcan be determined. These types of systems typically require very precisetiming. For example, since d=rt and r=3×10⁸ meters/second, in order tolocate something to within 1 meter, there is a requirement for 3.3×10⁻⁹(3 nanoseconds) of temporal accuracy for each distance calculation. Thismeans that the timing between the remote transmitter to be located andeach of three receivers, as well as the timing between all of thereceivers, must be known within 3 nSec. Various techniques have beenused with varying degrees of success to overcome this timing requirementbut all require fairly complex systems. Some use a centralized time baseand remote receiving antennas that must be connected with specialcoaxial cables.

Others use calibration transmitters whose location is precisely known tohelp compensate for timing jitter. All of these solutions requirecomplex, expensive infrastructure.

In the second technique, existing systems attempt to calculate thedistance between a transmitter and receiver based on a received signalstrength indication (RSSI).

While this is conceptually simpler then estimating location based ontime-of-arrival (TOA) it is plagued by the issue of multipath,especially in indoor spaces. The RSSI is a function of distance and apath-loss factor: RSSI=1/d^(−f), where d is distance and f is thefactor. However, the same radio wave travels over many paths between thetransmitter and receiver. Some times these multiple waves arrive at thereceiver in-phase (constructively) and some times they arriveout-of-phase (destructively). This means that the RSSI can be 3 dBhigher than the actual value or as much as 30 dB lower than the truevalue.

This multipath fading makes it extremely difficult to determine the RSSIvalue accurately. The second challenge is determining the path-lossfactor, f. Various techniques have been suggested to both compensate formultipath as well as the calculation of f. These typically involvecalibration signals, averages of RSSI over time or diversity receiversystems. The trade-off is that these techniques, while typically simplerthan the TOA calibration, lead to accuracies that are not as good as TOAbased systems. It should also be noted here that “simple” is a relativeterm and even RSSI based systems must be quite complex in order to haveacceptable accuracy.

In summary, existing solutions attempt to accurately locate the distancea transmitter is from a receiver. The accuracy of the determination ofthe location of a transmitter is driven by how accurately the distancescan be calculated (d₃, d₂ and d₃) between the transmitter and thevarious receivers (R₁, R₂ and R₃).

SUMMARY

Therefore, there is a need for a location system that can accurately andsimply locate a transmitter. Ideally, this system does not requireprecisely calculating the distances between the receivers andtransmitter. The present invention allows the location of transmitter tobe determined (approximated) without requiring its distance from areceiver to be precisely known. This means that the overall system canbe much simpler and hence less expensive.

The present invention provides a location system which allows locationto be determined without requiring precise calculations of distance andallows differing degrees of precision to be provided in the same system.

In accordance with a first aspect, a method for determining location ofan object comprises the steps of: for a receiver, estimating a firstzone within which a first transmitter is located; for remainingreceivers that can detect a given transmitter, each estimating a secondzone within which a first transmitter is located; and determining ifthere are overlaps in any of the zones.

In accordance with another aspect, a method for determining location ofan object comprises the steps of: determining a potential target area,and estimating a target location within the potential target area. Incertain embodiments, the step of determining a potential target areacomprises the steps of: identifying receivers that received a signalfrom a transmitter, generating one or more line segments connecting theidentified receivers, determining zones around identified receivers,generating lines through intersections of zones and the one ore morelines; and designating the area defined by secants as the potentialtarget area. In some embodiments the step of generating lines comprisesgenerating secants through the intersections between the line segmentsand the zones for each zone. In other embodiments, the step ofgenerating lines comprises generating tangents at the intersectionsbetween the line segments and the zones for each zone. The step ofestimating a target location within the potential target area maycomprise finding the center of the potential target area.

In accordance with another aspect, a method for determining location ofan object comprises the steps of: identifying receivers that received asignal from a transmitter, generating one or more lines segmentsconnecting the identified receivers, determining zones around theidentified receivers, generating lines through intersections of zonesand the one ore more line segments, designating the area defined by thelines as the potential target area; and determining center of potentialtarget area.

In accordance with another aspect, in a computing device, a method fordetermining location of an object, comprises the steps of for areceiver, estimating a first zone a first transmitter is in; forremaining receivers that can receive a given transmitter, eachestimating a second zone a first transmitter is in; and determining ifthere are overlaps in any of the zones.

In accordance with another aspect, in a computing device, a method fordetermining location of an object, comprises the steps of: identifyingreceivers that received a signal from a transmitter, generating one ormore line segments connecting the identified receivers, determiningzones around the identified receivers, generating lines throughintersections of zones and the one ore more line segments, designatingthe area defined by lines as the potential target area; and determiningthe center of the potential target area.

In accordance with another aspect, in a location system comprising atleast one transmitter and at least two receivers, a method comprises:determining which receivers can receive a signal from the transmitter,estimating the zones of the receivers the transmitter is in, determiningif there are overlaps in any of the zones.

In accordance with another aspect, a computer program product holdsinstructions executable in a computer for determining location of anobject. The instructions comprise the steps of for a receiver,estimating a first zone within which a first transmitter is located; forremaining receivers that can receive a given transmitter, eachestimating a second zone within which a first transmitter is located;and determining if there are overlaps in any of the zones.

In accordance with another aspect, a computer program product holdsinstructions executable in a computer for determining location of anobject. The instructions comprise the steps of identifying receiversthat received a signal from a transmitter, generating one or more linesegments connecting the identified receivers, determining zones aroundthe identified receivers, generating lines through intersections ofzones and the one ore more line segments, designating the area definedby lines as the potential target area, and determining the center of thepotential target area.

In accordance with another aspect, a location system for determininglocation of an object comprises a location determination module fordetermining a potential target area encompassing the object andestimating the location of the object within the potential target area.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be apparent from the description herein and theaccompanying drawings, in which like reference characters refer to thesame parts throughout the different views.

FIG. 1A illustrates a location system having an object identifier and alocation determining module according to an embodiment of the invention;

FIG. 1B illustrates a location system having a receiver and one or moretransmitters according to an embodiment of the invention;

FIG. 2 illustrates a location system according to another embodiment ofthe invention having a network connection element, one or more objectidentifiers and an optional fixed location identifier;

FIG. 3 illustrates an object identifier according to an embodiment ofthe invention;

FIG. 4 is a perspective view of an object identifier according to anembodiment of the invention;

FIGS. 5A-5C illustrate various methods of operation of an objectidentifier according to various embodiments of the invention;

FIG. 6 illustrates a network connection element according to anembodiment of the invention;

FIG. 7 illustrates a location system, according to a further embodimentof the invention, having a network connection element, one or moreobject identifiers, a location resolver, and an optional fixed locationidentifier;

FIG. 8 illustrates a location resolver according to an embodiment of theinvention;

FIG. 9 provides a method of operation of a location resolver accordingto an embodiment of the invention;

FIGS. 10-10F illustrate one method of determining location withoutrequiring precise distance calculations.

FIGS. 10G-10K illustrate another method of determining location withoutrequiring precise distance calculations.

FIG. 11 illustrates a fixed location identifier according to anembodiment of the invention;

FIG. 12 illustrates a location system according to a further embodimentof the invention;

FIG. 13 provides a perspective view of a location system installed at alocation according to a further embodiment of the invention; and

FIG. 14 illustrates a network interface for use in a network connectionelement or a location resolver according to an embodiment of theinvention

DETAILED DESCRIPTION

Various embodiments of the present invention provide apparatus andmethods for the determination of location information. Variousembodiments of the invention allow for location information tocommunicated over a network or over the Internet. Various embodiments ofthe invention may be configured to minimize installation efforts by theuse of various techniques such as using wireless components to providelocation information to fixed locations and by an ability in someembodiments of the invention to utilize existing wiring, already inplace in many environments.

A location system 10 is provided by way of example in FIG. 1A. Theillustrated location system 10 includes an object identifier 800 and alocation determining module 14. The object identifier 800 may be coupledto an object such that a location of that object corresponds to thelocation of the object identifier 800. The object identifier 800 may beany device capable of identifying a location of an object. According toan embodiment of the invention, an example includes an electronicdevice. Examples of electronic devices may be in many forms and include,by way of example, a processor, a computer, a personal digitalassistant, a communications device, such as a cell phone, a networkappliance, a web server, a network, any device capable of manipulatinginformation, a receiver, a transmitter, an interface or any combinationof these devices. A network may be a local area network (LAN), a widearea network (WAN), the Internet, an intranet, or a metropolitannetwork. The network may be a wireless network such as a Bluetoothnetwork, a cellular network, a GSM based network, a hard-wired network,or some other type of network.

According to various embodiments of the invention, the object identifier10 transmits two identifiers, one identifier corresponding to the objectidentifier 10 and a second identifier which is a group designator. Whilethe identifiers may be in many forms, some examples, according tovarious embodiments of the invention, include numbers, letters, URLs,MAC addresses and IP addresses.

According to an embodiment of the invention, the location determiningmodule 14 may include any structure suitable for determining location.Examples include any device with intelligence to determine the locationof one or more object identifiers. According to various embodiments ofthe invention, the location determining module 14 may include one ormore of each of the following, including combinations of the following:a network connection element, an object identifier, a fixed locationidentifier, a location resolver, a database, topology data, anelectronic device, a web interface, a network interface, a specializednetwork interface, an implementation interface, a database interface, anetwork and/or a specialized network, a receiver and/or a transmitter.According to various embodiments of the invention, the locationdetermining module 14 may have only a receiver, only a transmitter orboth a receiver and a transmitter. It will be apparent to one ofordinary skill in the art that one or more components may be distributedin a wide variety of configurations.

According to various embodiments of the invention, the present inventionmay be used to determine a location of a location determining module. Insuch an embodiment, the location determining module may be a mobilemodule, capable of determining its own location relative to one or moreobject identifiers. In such an embodiment, the object identifiers may befixed. Optionally, the object identifiers may be moving. One example ofthe use of a mobile location determining module involves a locationsystem configured to determine locations within a large area. If such alarge area is populated by a small number of objects, the components ofsuch a location system may be more efficiently configured by providingfunctionality of a location determining module with each object. In sucha case, object identifiers could be distributed throughout the largearea. The location determining module could then be adapted to receivelocation signals from the object identifiers and thereby determine alocation of the location determining module. In this embodiment, thelocation of the objects is determined relative to the location of theone or more object identifiers, although the locations of the objectidentifiers may be known, allowing locations of objects to be determinedrelative to other references or by name, such as a location on a map ora specific room.

The configuration above is contrasted with another embodiment of theinvention, better suited to environments with a greater number ofobjects in a smaller area. In such an embodiment, each object may beprovided with an object identifier. One or more location determiningmodules may then be located within the area to receive location signalstransmitted by the object identifiers. In this embodiment, the locationof the objects is determined by determining the location of the objectidentifiers.

According to various embodiments of the invention, the locationdetermining module 14 may be capable of performing additionalfunctionality, such as receiving requests for information, providinginformation, storing information, commanding actions in response tolocation information, associating objects with other objects or withlocations, establishing privacy conditions regarding availability oflocation information, interfacing directly with various network types,and the like. According to further embodiments of the invention, thelocation determining module 14 includes multiple, distributed receivers,some of which may be connected to a network, and others not connected toa network. According to various embodiments of the invention, the objectidentifier 10 and location determining module 14 utilize both RF signalsand IR signals for the determination of location.

According to an embodiment of the invention, the location determiningmodule 14 may include one or more databases. The databases may storeinformation relating to current location of object identifiers, fixedlocation identifiers and network connection elements.

According to various embodiments of the invention, the invention may beused only within an enclosed structure. Enclosed structures includebuildings, such as office buildings, exhibition halls, health careinstitutions, homes or other structures. According to other embodiments,the invention may be used outside of enclosed structures or may be usedboth within and outside enclosed structures.

According to an embodiment of the invention, a location system 100 isprovided. As illustrated by way of example in FIG. 1B, the locationsystem 100 is provided with a transmitter 200 and a receiver 300.Optionally, additional transmitters 200 (shown in phantom) may beprovided. The transmitter 200, for example, can form part of the objectidentifier 800, and the receiver 300, for example, can form part of thelocation determining module 14. A transmitter 200 communicates with thereceiver 300 in order to provide a signal for receipt by the receiver300. According to one embodiment of the invention, the transmitter 200transmits a signal using only a radio frequency (RF) transmitter 210. Insuch an embodiment, the receiver 300 is provided with an RF receiver310. According to a further embodiment of the invention, the transmitter200 may be provided only with an infra red (IR) transmitter 220 totransmit an IR signal. In such an embodiment the receiver 300 isprovided with an IR receiver 320. According to a further embodiment ofthe invention the transmitter 200 is provided with both an RFtransmitter 210 and an IR transmitter 220 while the receiver 300 iscorrespondingly provided with both an RF receiver 310 and an IR receiver320. According to this embodiment, both the RF signal and the IR signalare used for the determination of the location of the transmitter 200.According to one practice, the RF signal can include information uniqueto the object identifier or the object to which it is attached. The IRsignal can be non-unique and not include any specific information.

According to a further embodiment of the invention, the receiver 300 maybe provided with a network interface 330. An example of the networkinterface 330 includes an interface for a local area network (LAN) oranother interface to allow direct coupling of the receiver 300 to anetwork 400. According to one embodiment of the invention the networkinterface 330 is comprised of an interface capable of direct coupling ofthe receiver to a UTP-based, Ethernet network interface. The Ethernetnetwork may be a wired or wireless network or a combination thereof.

According to another embodiment of the invention the receiver 300 isprovided with a web server 340. The web server 340 may be configured toprovide location information directly to the network 400 and/or theInternet 500. The web server 340 may also be configured to allow forcontrol or configuration of the receiver 300 through the network 400and/or the Internet 500.

According to one practice, the receiver 300 can be configured to conveysignals to the network 400 in a periodic or intermittent manner. By wayof example, the receiver 300 can convey information in any appropriateformat, such as a data packet, to the network 300 every selected timeperiod. The time period can preferably be between 1 second and 10minutes, more preferably between 5 seconds and 1 minute, and mostpreferably every 10 seconds. The signals generated by the receiver areindependent of receipt of signals from an object identifier. That is,the generation of signals by the receiver is periodic and not inresponse to receipt of a signal by the receiver.

As shown by way of example, a location determining module 14, accordingto an embodiment of the invention, is illustrated, by way of example, asincluding the network 400.

A further embodiment of the invention is illustrated in FIG. 2. Alocation system 700 is illustrated by way of example having an objectidentifier 800 in communication with a network connection element 900.According to an embodiment of the invention, the object identifier 800is physically coupled to an object so that the location of the objectidentifier 800 is considered to be the location of the object. Accordingto another embodiment of the invention, the location of the object maybe determined by locating one or more object identifiers 800 in an areaand coupling a network connection element 900 to an object. In such anembodiment, the location of the network connection element 900, andhence the object, is determined relative to the one or more objectidentifiers 800. The network connection element 900 is configured to becoupled to a network 400. According to an optional embodiment of theinvention, the network may be a wireless network. As illustrated in FIG.2, one or more object identifiers 800 communicate to the networkconnection element 900. According to another embodiment of theinvention, the network connection element 900 may communicate back tothe object identifier 800.

According to a further embodiment of the invention a fixed locationidentifier 1000 is provided. The fixed location identifier 1000 isconfigured to receive signals from one or more object identifiers 800and retransmit that information. The retransmitted information may bereceived by the network connection element 900. According to oneembodiment of the invention the retransmitted information includes theinformation provided by the object identifier 800, coupled withadditional information to identify the fixed location identifier 1000that is re-transmitting the information. According to an embodiment ofthe invention, plurality of network connection elements 900, fixedlocation identifiers 1000 and object identifiers 800 may be provided inthe location system 700. In such a case, the network 400 may providecommunication among the network connection elements 900 in order todetermine the location of one or more object identifiers 800 by one ormore network connection elements 900 or by the use of other devicescoupled to the network 400.

As shown by way of example, a location determining module 14, accordingto an embodiment of the invention, is illustrated, by way of example, asincluding the network connection element 900, the fixed locationidentifier 1000 and the network 400.

According to an embodiment of the invention, the object identifier 800and/or fixed location identifier 1000 transmits various information.According to an embodiment of the invention, this information istransmitted over both RF and IR signals. Optionally, the information maybe transmitted over only one signal. According to an embodiment of theinvention, examples of the information transmitted may include one orall of the following: RF power level; IR power level; battery level;input device status; transmission frequency, e.g. repetition rate, forany or all types of transmissions, such as IR and/or RF; an identifiercorresponding to the transmitting device; an identifier corresponding toa group to which the transmitting device is associated; any informationreceived from another system component; status or condition information;or the like. According to an embodiment of the invention, someinformation may be repeated over multiple signal transmissions. Examplesinclude transmitting input device status over ten transmissions toincrease the likelihood of receipt by other components of the locationsystem.

The object identifier 800 according to an embodiment of the invention isillustrated by way of example in FIG. 3. The object identifier 800 isprovided with a controller 810 and controller support 820. Thecontroller support 820 may include various items such as a power supply,such as a battery or other apparatus to provide electrical power, memoryand/or various time keeping circuitry such as an oscillator. Controllersupport 820 may optionally include non-volatile memory. Variouscomponents of the controller support 820 may optionally be incorporatedinto the controller 810 or may be provided from an external source,outside the object identifier 800.

According to an embodiment of the invention, the object identifier 800may be provided with an RF transmitter 830. According to a furtherembodiment of the invention the object identifier 800 may be providedwith an IR transmitter 840. According to an further embodiment of theinvention the object identifier 800 is provided with both an RFtransmitter 830 and an IR transmitter 840.

According to another embodiment of the invention, the object identifier800 is provided with an RF receiver 850. According to another embodimentof the invention the object identifier may be provided with an IRreceiver 860.

The object identifier 800 may also be provided with an input device 870.Examples of input devices include buttons, switches, keypads, ports forelectrical or optical communication with other devices, sensors, such asphoto cells cameras or microphones. Other types of input devices 870 maybe apparent to one of ordinary skill in the art upon reading thisdisclosure and are to be considered within the scope of the invention.One or more input devices 870 are configured to provide input to thecontroller 810 in order to allow the controller 810 to take an action,not take an action, or to forward information outside the objectidentifier 800 by way of an RF transmitter 830 and/or an IR transmitter840.

According to a further embodiment of the invention an indicator 880 maybe provided to enable the controller 810 to output information in theproximity of the object identifier 800. Examples of indicators 880include visual, audio and vibrational devices. Examples of these includebuzzers, bells, horns, LEDs, other forms of lights and/or displays. Theindicator 880 may be configured to display or output informationdetermined by the controller 810 or received by the controller 810through the input device 870, RF receiver 850 and/or the IR receiver860.

An object identifier 800 is illustrated by way of example according anembodiment of the invention, in FIG. 4. The object identifier 800 isillustrated with two indicators 880 in the form of two LEDs. Three inputdevices 870 are also illustrated in the form of switches. Two switchesare illustrated so as to correspond to the two indicators 880, while thethird switch 870 is illustrated on an opposing surface of the objectidentifier 800. According to this illustrative embodiment, the inputdevice 870 on the lower surface of the object identifier 800 is normallypushed in when the object identifier 800 is attached to an object. Uponremoval from the object, the input device 870 extends, resulting in achange of position of the input device 870. This embodiment allows thecontroller 810 to be alerted when the object identifier 800 is removedfrom an object. Each of the indicators 880 may be configured toilluminate upon the activation of the corresponding switches, inputdevices 870, so as to allow visual confirmation of the activation of oneof the switches. Various uses of these switches will become apparent toone of ordinary skill in the art. Several examples, by way ofillustration, include panic alerts, causing the processor 810 to emit aspecialized signal through at least one of the RF transmitter 830 andthe IR transmitter 840. A further example may involve an ability toconfigure a portion of the location system 700 remotely by theactivation of the input devices 870.

FIGS. 5A, 5B and 5C illustrate, according to various embodiments of theinvention, various examples of a transmission of signals from the objectidentifier 800. A first method 802 is illustrated in FIG. 5A accordingto an embodiment of the invention. An RF power level is set to PN, step804. An IR signal is transmitted, step 806. The delay of m seconds thenoccurs, step 808. An RF signal is transmitted, step 812. A further delayof x seconds occurs, step 814. Pn is then incremented, step 816.

This method 802 provides a substantially consistent IR power level,while varying an RF power level. Varying the RF power level may assistin determining a location of the object identifier 800 by enabling thenetwork connection element 900, location determining module 14, orreceiver 300, to receive less than all of the RF signals.

According to an embodiment of the invention, one or both of the IR andRF signals are also transmitting information. Examples of thisinformation may include the signal strength being transmitted, theperiod between transmissions, the length of time of the transmissions,various identifiers, corresponding to the object identifier 800,information received from one or more input devices 870 and/or variousstatus information, such as those pertaining to the controller 810controller sport 820 or other components of the object identifier 800.According to one embodiment of the invention the RF signal istransmitted every ten seconds and the IR signal is transmitted everytwenty seconds.

Determination of the frequency and length of the transmissions involvesconsiderations including battery life precision of location, frequencyof updates to location, interference among signal transmissions andnetwork traffic.

A further method 822 of an embodiment of the invention is illustrated inFIG. 5B. According to this embodiment, an RF signal is transmitted, step824 and a delay, step 826 occurs before the next transmission of an RFsignal, step 824. Independently of the RF transmission, an IR signal istransmitted, step 828. The IR transmission, step 828 may occursimultaneously with the transmission of the RF signal, step 824 but thisembodiment of the invention is not so limited. The transmission of theRF signal, step 828 may occur at any time relative to the transmissionof the RF signal step 824. A delay of c seconds step 832, occurs beforethe next transmission of the RF signal, 828.

According to a further embodiment of the invention, a further method 842is illustrated by way of example in FIG. 5C. According to thisembodiment, an RF signal is transmitted, step 844 and an IR signal istransmitted, step 846. According to an alternative embodiment, atransmission in another medium may also occur, step 848. Examples ofother mediums include ultra-sonic (US), visual light, or audible sound.According to the method 842 of FIG. 5C, transmissions may be continuous,variable or occur at regular intervals. The transmissions among variousmediums may be synchronized or random relative to transmissions in othermediums.

An example of a network connection element 900 according to anembodiment of the invention is illustrated in FIG. 6. A networkconnection element 900 includes many component similar to those of theobject identifier 800 illustrated by way of example in FIG. 3. A networkconnection element 900 is provided with a controller 910 and acontroller support 920. Controller support 920 may optionally includenon-volatile memory. Optionally, various embodiments of the inventionmay include one or more of the following in the network connectionelement 900: an RF receiver 930, an IR receiver 940, an RF transmitter950, an IR transmitter 960, an input device 970 and/or an indicator 980.

The network connection element 900 is adapted to receive signals fromthe object identifier 800. According to an embodiment of the invention,the network connection element 900 contains hardware and softwarecapable of receiving signals from other components of the locationsystem, such as object identifiers 900, other network connectionelements 900. According to an embodiment of the invention, the networkconnection element 900 may have network connectivity software, a localweb server, object identifier analysis software, software to transmitthe results of an object identifier analysis to a remote server, DHCPsoftware and local permanent storage. According to an embodiment of theinvention, the network connection element 900 may also includeconfiguration, service and debug applets to be used in the maintenanceand configuration of the object identifier 900.

The network connection element 900, according to an embodiment of theinvention, may further be provided with a web server 990. As with theweb server 340 of the receiver 300 of location system 100, web server990 of network connection element 900 is able to provide or receiveinformation or commands. In various embodiments of the invention, theweb server 990 may allow for control and configuration of any componentof the location system.

According to a further embodiment of the invention, the networkconnection element 900 may be provided with a network interface 992. Thenetwork interface 992, as with the network interface 330 of locationsystem 100, is configured to couple the controller to a network 400.According to an embodiment of the invention, the network interface 992is adapted to packetize buffered information received and send thisinformation as a group, thereby providing more efficient network usagein some applications.

A further embodiment of the invention provides a database 996 incommunication with then controller 910 of the network connection element900. The database 996 may be provided within the network connectionelement 900 or may be provided on a network 400. According toalternative embodiment of the invention, the database 996 may beprovided within the network connection element 900 and also in directcommunication with the network 400.

According to a further embodiment of the invention, a location system710 is illustrated by way of example in FIG. 7. According to thisembodiment, a location resolver 1100 l is provided for communicationwith the network connection element 900. In this embodiment, thelocation resolver 1100 communicates with one or more network connectionelements 900 to obtain information pertaining to the location of one ormore object identifiers 800 and one or more optional fixed locationidentifiers 1000. The location resolver 1100 may be provided in the formof software or hardware or a combination of both. The location resolver1100 may communicate with one or more network connection elements 900over a network 400.

As shown by way of example, a location determining module 14, accordingto an embodiment of the invention, is illustrated, by way of example, asincluding the network connection element 900, the location resolver 1100and the fixed location identifier 1000. In this embodiment, the network400 is not included in the location determining module 14, butoptionally communicates with the location determining module 14.

The location resolver 1100, according to an embodiment of the invention,is further illustrated by way of example in FIG. 8. As shown in FIG. 8,a controller 1110 is provided in communication with a network interface1120. The network interface 1120 is adapted to be coupled to the network400. Controller support may also be optionally provided. A web server1130 is provided in communication with a controller 1110. The web server1130 of the location resolver 1100 is similar to the web server 990 ofthe network connection element 900, discussed herein.

According to an embodiment of the invention, the location resolver 1100may be provided with a configuration capability to configure othercomponents of the location system. For example, an embodiment of thelocation resolver 1100 may perform some or all of the followingfunctions: reset system time; reset communications; disable all orselected input devices of all or selected components, such as objectidentifiers, fixed location identifiers, network connection elements;establish and/or cancel associations between all or selected components;establish and/or cancel privacy settings for specific locationinformation; configure network communication protocols; configurereceiver and/or transmitter configurations, altering or eliminatingsignals, signal types, such as RF, IR, ultrasonic, or the like, ortransmission frequencies and the frequencies at which transmissions areexpected.

An implementation interface 1140 is also provided in communication withcontroller 1110. The implementation interface 1140 is provided tocommunicate with other devices in order to allow for the communicationof location information and/or initiation or response to commands asdescribed herein. Various examples of implementation interfaces 1140include XML and SMTP protocols, other examples may be apparent to thoseof ordinary skill in the art.

A database 1150 is also provided either within the location resolver1100 or external the location resolver 1100. The database 1150 isadapted to store information relating to the location of one or moreobject identifiers 800 and/or optional fixed location identifiers 1000and/or network connection elements 900. According to various embodimentsof the invention, the database 1150 may store current and/or previouslocation and status information of location system components,associations of location system components with each other or locations,privacy protocols and status, topology data indicating locations of someor all location system components relative to each other, or in otherdescriptive terms, such as room or location names or by a coordinatesystem.

A database interface 1155 may be provided in another embodiment of theinvention in order to facilitate interaction between the database 1150and the controller 1110. The database interface 1155 may be a network orother hardware or software to controller 1110 to enable the controller1110 to access the database 1150. Various examples of databaseinterfaces 1155 include JDBC and ODBC, other examples may be apparent tothose of ordinary skill in the art.

A method 1102 of operation of the location resolver 1100, according toan embodiment of the invention is illustrated in FIG. 9. The locationresolver 1100 initially waits for input from a receiver, such as thenetwork connection element 900, step 1104. The location resolver 1100then determines whether an IR signal was received, step 1106. If an IRsignal was received, data received from the transmitter and receiverslocation is made available, step 1108. If an IR signal is not receivedthe location resolver 1100 checks to see if an RF signal was received,step 1112. Location resolver 1100 also checks to see if an RF signal wasreceived after making any data available from the reception of an IRsignal available, step 1108. If an RF signal was not received, thelocation resolver 1100 according to an embodiment of the inventionreturns again to wait for further input from the network connectionelement 900. If an RF signal was received, the location resolver 1100determines whether the RF power was high, step 1114. If so, datareceived from the transmitter is made available with message indicatingthat the object identifier is within a large radius of the networkconnection element 900, step 1116. If the RF signal power was not highthe location resolver 1100 determines whether the RF power was medium,step 118. If so, data received from the object identifier is madeavailable with a message that the object identifier is within a smallerradius of the network connection element 900, step 1122. If the RFsignal power was not medium the location resolver 1100 determineswhether the RF signal power was low, step 1124. If so data from theobject identifier 800 is made available with an indication that theobject identifier is within a smaller radius of the network connectionelement 900, step 1126. The location resolver 1100 then returns to awaitfurther input from one or more of the network connection elements 900,step 1104.

It is understood that the method of FIG. 9 may be accomplished by usingtransmitters that vary in output power or by constant power outputtransmitters. In using constant power output transmitters, receivedsignal strength is categorized according to signal strength, such as bythe use of a histogram. According to an embodiment of the invention, thenetwork connection element 900 classifies signal strength withinspecific ranges and may pass an indication of the appropriate range toother location system components. According to another embodiment of theinvention, the network connection element 900 provides a signal strengthvalue that may be passed to other location system components, such thelocation resolver 1100, allowing more precise analysis of receivedsignal strength information.

According to one embodiment of the invention, RF and IR signal strengthare adjusted to a range of approximately 20 feet. Other embodiments ofthe invention may involve adjusting signal strength of RF and/or IRand/or other signal types, such as ultrasonic, ranges to a few inches,feet, thousands of feet, or miles. Another embodiment of the inventioninvolves varying signal strength among various types of objectidentifiers.

A method of operation of the location resolver 1100 involvesmultilateration. Multilateration determines location by the use ofdetermining range from a relative location. Multilateration can beperformed by a single receiver, but is best accomplished by multiplereceivers. An object can infer the location of another object bycalculating its range from one or more beacons with known locationsusing some type of signal measurement. According to an embodiment of theinvention RF signal strength is used to determine location. According toa further embodiment both RF and IR are used to determine location. Itis understood that an absence of a signal that is expected is considereda signal for purposes of determining location. An example, for purposesof illustration, is the receipt of an RF signal but not an IR signal mayindicate a transmitter out of IR range but within RF range, or just outof line-of-sight if required for lower-powered IR transmissions. Thereceiver may be configured to expect both RF and IR transmissions atspecific intervals generally or for a specific transmitter. This is oneexample of the use of both RF and IR for determination of location.

In addition to current signal information, other information may be usedin determining location. Previous location information may also be usedin determining current location. Locations of other location systemcomponents may also be used in determining location. For example,locations of one or more network connection elements 900, one or morefixed location identifiers 1000 and other object identifiers 800 may beused in determining location of a particular location system component.According to one embodiment, establishing relative distances betweenadditional nearby components and the component for which locationinformation is desired assist in establishing a location with greaterparticularity.

According to an embodiment of the invention, transmission rates may varyamong different types of object identifiers. Transmission rates may beadjusted in relation to the type of object for which locationinformation is desired. Examples include low transmission rates forobjects typically stationary, such as equipment typically found in aparticular room. Whereas people, or mobile equipment may be bettertracked by more frequent signal transmissions.

Another method of determining location involves at least one Bayesiannetwork. A further method of determining location involvestriangulation. An example of one or more of the foregoing methodologiesare described, for example, in U.S. Pat. No. 5,774,876, which isincorporated herein by reference. Bayesian networks are also describedin Castro, Paul et al. “A Probabilistic Room Location Service forWireless Networked Environments” In: Ubicomp 2001: Ubiquitous Computing,Third International Conference, Atlanta, Ga., USA, Sep. 30-Oct. 2, 2001Proceedings. Edited by G. D. Abowd, et al. Heidelberg, Germany:Springer-Verlag, 2001, LNCS 2201, p. 18 ff. This publication isincorporated herein by reference. Combinations of these methods or othermethods of location determination may be apparent to one of ordinaryskill in the art and are included within the scope of the invention.

Another technique determines a location of a transmitter withoutrequiring the distance from the object identifier to one or morereceivers to be precisely known. This means that the overall system canbe much simpler and hence less expensive. This technique involvesdetermining a potential target area and then estimating a targetlocation within the potential target area. Two methodologies foraccomplishing this are provided below. The first methodology looks foroverlaps between zones of receivers to define the potential target areaand is illustrated in FIGS. 10-10F. The second methodology determines apotential target area without requiring overlapping zones and isillustrated in FIGS. 10G-10K. It should be noted that the twomethodologies discussed below, or any the other methods discussed inthis disclosure, are not mutually exclusive. Techniques from any ofthese methods may be combined.

In the first methodology, an example illustration 1002 of which is shownin FIG. 10, there are two receivers, R₁ 1004 and R₂ 1006, and threetransmitters T₁ 1008, T₂ 1012 and T₃ 1014. There are three rings (zones)around each receiver: Zn-m where n is the designator for the receiverand m is the designator for the zone. Although three zones areillustrated in FIG. 10, those of ordinary skill will readily recognizethat any number of zones can be used. More zones lead to higherprecision but more complex calculations. In the example embodiment, thezones are actually three dimensional, but can also be two dimensional.

According to the illustrated embodiment of FIG. 10A, the steps to locatea transmitter are set forth. First, for a given receiver, the systemestimates the zone where a given transmitter is located 1016. This maybe accomplished according to any suitable technique, including, butlimited to RSSI, TOA. The system continues to estimate zones until allthe receivers that can receive a signal from a given transmitter havetheir zones determined. This yields a vector (Zn-m)₁, (Zn-m)₂, (Zn-m)₃ .. . (Zn-m)_(P) where P is the number of receivers that can hear a giventransmitter 1018. The system then determines or calculates if there areoverlaps in any of the determined zones 1022.

So, in the above example, T₃ can be located quite precisely because itis located in the potential target area defined by the overlappingregion of zones Z₁₋₂ and Z₂₋₁, which is relatively small. Transmitter T₁can also be located quite precisely because it is in the potentialtarget area defined by the overlap of zones Z₁₋₁ and Z₂₋₁, which alsohave a small overlapping area. The system meanwhile locates transmitterT₂ somewhere within zone Z₂₋₁.

Note that the above example is a fairly simple case. A more generalexample is described below. Assume that there are N spheres and that theposition (x, y, z), outer radius (R) and wall thickness (t) are known.The goal of the calculation is to find the area of intersection betweeneach sphere. Then, the total area of intersection between all of thespheres can be obtained by adding the intersection areas for theindividual spheres.

The approach in this example is to determine if spheres are intersectingby calculating the distance between the centers of the spheres andcomparing that distance to the radius of the spheres. For any twospheres (j and k), the distance equation is:d _(jk) ={square root}{square root over (x _(j) −x _(k) ) ² +(y _(j) −y_(k) ) ² +(z _(j) −z _(k) ) ² )}

The two spheres are interacting only if d_(jk)≦(R_(j)+R_(k)). Similarly,three spheres (j, k, m) are mutually intersecting ifd_(jk)≦(R_(j)+R_(k)), d_(jm)≦(R_(j)+R_(m)), and d_(km)≦(R_(k)+R_(m)).This can be continued for four (or more) spheres, but it is unlikelythat more than four spheres mutually intersect, unless the size range isvery large and a sphere can be enveloped by another sphere. Forconvenience, each of these types of mutual interactions can beclassified separately, as:

Case 0: no interaction

Case 1: interaction between two spheres

Case 2: mutual interaction between three spheres

Case 3: mutual interaction between four spheres.

Case 0 is trivial since the area is zero. A solution for theintersection area for case 1 is below. Cases 2 and 3 become morecomplicated, particularly when the radii of the spheres are different.Until those cases are solved, a good first approximation is to assumethat the correction for the mutual interaction between more than twospheres is negligible. This is a good assumption if d_(jk) is onlyslightly less than (R_(j)+R_(k))

For Case 1, consider the geometry of 10B. The intersection area 1024 istaken at the interface between the two spheres 1024 and 1026, and is ina plane perpendicular to the line 1028 connecting the centers of thespheres. This area A 1024 has a circular shape of radius a and can becalculated from the geometry as$A = {\frac{\pi}{4d_{jk}^{2}}\left\lbrack {{4R_{j}^{2}R_{k}^{2}} - \left( {d_{jk}^{2} - R_{j}^{2} - R_{k}^{2}} \right)^{2}} \right\rbrack}$

This equation even applies for larger interactions, as shown in FIG.10C, where both walls are effectively penetrated but the center ofeither sphere has not yet reached the plane of the interface area. FIG.10D shows the center region of the smaller sphere reaching the plane ofthe intersection area, while FIG. 10E shows the center region of alarger sphere reaching the plane of the intersection area. In eithercase, the intersection area will be reduced by the area of the gap ofthe center region of the sphere that breaks the interface plane, or itwill be increased because of the curved spherical surface area.Similarly, FIG. 10F shows that the common wall between the two sphereshas disappeared. The interface area can include the common plane betweenthe two spheres (dashed) but may also include the curved inner surfaceof the smaller sphere. Whether or not these-situations need to beconsidered is optional.

In the present example, for an initial treatment, only the planar areaof intersection will be treated. These areas can then be expressed as:$A = \left\{ \begin{matrix}{{{{\pi\left\lbrack {R_{k}^{2} - \left( {R_{k} - t_{k}} \right)^{2}} \right\rbrack}\quad R_{j}} > R_{k}};{\sqrt{\begin{matrix}{R_{k}^{2} - {\frac{1}{4d_{jk}^{2}}\left\lbrack {{4R_{j}^{2}R_{k}^{2}} -} \right.}} \\\left. \left( {d_{jk}^{2} - R_{j}^{2} - R_{k}^{2}} \right)^{2} \right\rbrack\end{matrix}} < \left( {R_{k} - t_{k}} \right)}} \\{{{{\pi\left\lbrack {R_{j}^{2} - \left( {R_{j} - t_{j}} \right)^{2}} \right\rbrack}\quad R_{j}} > R_{k}};{\sqrt{\begin{matrix}{R_{j}^{2} - {\frac{1}{4d_{jk}^{2}}\left\lbrack {{4R_{j}^{2}R_{k}^{2}} -} \right.}} \\\left. \left( {d_{jk}^{2} - R_{j}^{2} - R_{k}^{2}} \right)^{2} \right\rbrack\end{matrix}} < \left( {R_{j} - t_{j}} \right)}}\end{matrix} \right.$

These assume that the j sphere has a larger radius than the k sphere.The upper case applies when c≦(R_(k)−t_(k)) while the lower case applieswhen b≦(R_(j)=t_(j)). These equations are valid as long as the smallersphere is outside the bigger sphere or d_(jk)≦R_(j). However, thisconstraint can be relaxed slightly so that c>0.

For completeness, the expressions for a, b, and c are:$a = {\frac{1}{2d_{jk}}\sqrt{{4R_{j}^{2}R_{k}^{2}} - \left( {d_{jk}^{2} - R_{j}^{2} - R_{k}^{2}} \right)^{2}}}$$b = {\sqrt{R_{j}^{2} - a^{2}} = \sqrt{R_{j}^{2} - {\frac{1}{4d_{jk}^{2}}\left\lbrack {{4R_{j}^{2}R_{k}^{2}} - \left( {d_{jk}^{2} - R_{j}^{2} - R_{k}^{2}} \right)^{2}} \right\rbrack}}}$$c = {\sqrt{R_{k}^{2} - a^{2}} = \sqrt{R_{k}^{2} - {\frac{1}{4d_{jk}^{2}}\left\lbrack {{4R_{j}^{2}R_{k}^{2}} - \left( {d_{jk}^{2} - R_{j}^{2} - R_{k}^{2}} \right)^{2}} \right\rbrack}}}$

As a special case, the sphere can be assumed to have an equal diameter.This provides much simpler expressions but may not be applicable.

Another method of determining (approximating) the location of atransmitter can be seen in FIG. 10G. This method 1032 comprises thesteps of determining a potential target area (PTA) 1034 and thenestimating a target location within the PTA 1036. This method isparticularly useful in the situation mentioned above wherein there is nooverlap between zones. Zones may not overlap due to interference in thetransmitter signal but an approximation can still be made.

A more detailed flow chart of this method is shown in FIG. 10H. The stepof determining the PTA 1034 further comprises the steps of identifyingthe receivers that have received a signal from a transmitter 1038,generating one or more line segments connecting the receivers 1042,determining zones around the receivers 1044, generating lines throughthe points where the lines intersect the zones 1046. The area containedby the lines defines the PTA. In this example, estimating the targetlocation within the PTA 1036 is accomplished by finding the center ofthe PTA. On skilled in the art will recognize there are several methodfor finding the center of the PTA

An example where there are two receivers with zones that do not overlapcan be seen in FIG. 10I. First, the two receivers 1048 are identified asreceiving a signal. Then a line segment 1054 is generated between thereceivers. Then the zones 1056 of the receivers are determined. Thenlines (here tangents because there is only one intersection on eachzone) are generated at the intersection of the line and the zones 1062.The area bounded by the tangents , in this case the line connecting thereceivers, is the PTA. The center of the PTA, here found along the lineconnecting receivers provides a good approximation of the targetlocation of the transmitter 1064.

An example with three receivers with non-overlapping zones is shown inFIG. 10J. First the receivers receiving a signal are identified 1058.Then line segments are generated between the receivers 1064. Then thezones 1066 are determined. Next, lines, here secants, are generatedthrough the intersections of the line segments and the zones 1068. Thearea bounded by the secants defines the PTA 1072. Determining orestimating the approximate or exact center of the PTA provides a goodapproximation of the target location of the transmitter 1074.

This method also works when the zones overlap. An example of such asituation is shown in FIG. 10K. Here, the same method is applied and thePTA 1076 and approximation of the target location of the transmitter1078 are found within the area of overlap as discussed above. Thismethod may also be used when there is a combination of overlapping andnot overlapping zones.

Privacy conditions may be established regarding location information forone or more location system components. Privacy may be accomplished in avariety of ways. For example, privacy may be accomplished by not makinglocation information available or by not determining locationinformation. Privacy may be managed by an opt-out protocol, requiring anaction to establish privacy. Privacy may be managed by an opt-inprotocol, requiring an action to cancel privacy. A not-opt-out protocolmay also be used, preventing action from establishing privacy. Variousprotocols may be used in combination within a location system. Differentlocation system components may subject to different protocols. Examplesinclude various groups of object identifiers being subject to differentprotocols, such as some people able to select a privacy protocol or aprivacy status, such as privacy or no privacy, while object identifiersused to locate equipment may be subject to a not-opt-out protocol.According to an embodiment of the invention, protocols or privacy statusmay be assigned through a batch-processing capability in a userinterface. According to another embodiment, privacy status for opt-in oropt-out protocols may be accomplished by an input device incorporated inthe location system component. Optionally, privacy status may beconfirmed by an indicator incorporated in the location system component.

Associations associating objects with other objects or with locationsmay be established. Examples of the use of associations include:determining procedure times, room utilization, proximity alerts that maybe used to alert a fall of a person, regulatory compliance, person &equipment associations; location & equipment associations; friend & foeassociations, and automatic billing. According to an embodiment of theinvention, association information may be stored in a database.Associations may be performed through a batch-processing capability in auser interface. According to another embodiment, associations may beaccomplished by an input device incorporated in the location systemcomponent. Optionally, association status may be confirmed by anindicator incorporated in the location system component. One exampleinvolves activating an input device on an object identifier, fixedlocation identifier or network connection element. An indicatorindicates, such as by an LED or sound, that association can beperformed. An input device may then be activated within a limited timeon another location system component, such as an object identifier, toestablish an association between the components.

Events or actions may be initiated based on location informationassociation information or input device status, or changes in any ofthese. One example involves sending information in response to an objectidentifier being within a range of locations or a specific location. Anexample includes paging a doctor when a specific patient enters atreatment area. Other examples of actions include entering informationin a database, sending XML data containing the current location data andstatus of a location system component onto the network. An example isthe use of a cardiac monitoring application typically used in a healthcare institution for receiving a report of a cardiac arrest. The termhealth care institution, as used herein, includes a wide variety offacilities associated with providing health care or services. Examplesinclude hospitals, managed care facilities, assisted care facilities andclinics. The location system according to an embodiment of the inventionmay be configured to receive a request for the location of a particularpatient, or the cardiac monitoring equipment sounding the alarm. Thelocation system can then automatically reply with location informationto assist health care institution staff in locating the patient in need.A similar example could use the activation of an input device on anobject identifier as a distress call by a patient, with the alert andlocation information forwarded to a health care institutioncommunication system for prompt attention by health care institutionstaff. One embodiment of the invention may interface with a Winegardinterface to unlock a door, or activate other security equipment, inresponse to location information or input device status. Other examplesinclude pages, WAP messages, sending e-mails and activating or cancelingalarms.

According to an embodiment of the invention, the components of thelocation system do not retransmit signals if they are not received. Bywaiting until the next scheduled transmission, transmissions throughoutthe location system area are reduced and interference difficulties arereduced.

The fixed location identifier 1000, according to an embodiment of theinvention is illustrated by way of example in FIG. 11. The fixedlocation identifier 1000 is similar to the object identifier 800illustrated and described in relation to FIG. 3. A controller 1010 isprovided in communication with controller support 1020. RF and IRtransmitters and receivers 1030, 1040, 1050, 1060 may be providedindividually or in combination according to various embodiments of theinvention. An input device 1070 and indicator 1080 may also each or bothbe included in various embodiments of the invention. The fixed locationidentifier 1000 is configured to receive signals from one or more objectidentifiers 800, and/or other fixed location identifiers 1000, andretransmit these signals to a network connection element 900 along withidentifying information to designate which of the fixed locationidentifiers 1000 is retransmitting the information. Additionalinformation relating to the retransmitting fixed location identifier1000 may also be appended, such as battery information or other statusinformation allowing remote monitoring of the fixed location identifier1000.

According to various embodiments of the invention, the fixed locationidentifier 1000 may be provided with input devices 1070 or indicators1080 to enable input information or various signaling functionality.Fixed location identifiers 1000 do not need to be coupled to othercomponents by the use of wiring or other infrastructure. Therefore, theuse of fixed location identifiers 1000 enable a location system to beimplemented with fewer network connection elements, as fixed locationidentifiers can provide additional information as to the location ofobject identifiers 800. Furthermore, fixed location identifiers 1000,can extend the range of network connection elements 900 by providing anoptional higher power transmission signal to reach network connectionelements 900 at ranges that object identifiers 800 may be incapable ofreaching.

The network connection element 900 is adapted to receive signals fromthe fixed location identifier 1000 as described above in relation tosignals from the object identifier 800. According to an embodiment ofthe invention, the network connection element 900 contains hardware andsoftware capable of receiving signals from the fixed location identifier1000. According to an embodiment of the invention, the networkconnection element 900 may have network connectivity software, a localweb server, fixed location identifier software, software to transmit theresults of a fixed location identifier analysis to a remote server, DHCPsoftware and local permanent storage. According to an embodiment of theinvention, the network connection element 900 may also includeconfiguration, service and debug applets to be used in the maintenanceand configuration of the fixed location identifier 1000.

A location system 720, according to a further embodiment of theinvention, is illustrated by way of example in FIG. 12. The locationsystem 720 includes various object identifiers 800, network connectionelements 900 and fixed location identifiers 1000. A network 400 isillustrated along with a database 1150 and location resolver 1100.According to the present embodiment, a topology database 1152 isseparately provided from the database 1150. The topology database 1152may be provided with information pertaining to the locations of networkconnection elements 900 and fixed location elements 900 and fixedlocation identifiers 1000. Such topology information allows for moredescriptive data to be provided regarding the location of objectidentifiers 800. For example, the location of a fixed locationidentifier 1000 or network connection element 900 may be specified as aparticular office, hallway or area. Therefore, if an object identifier800 is identified as within a small radius of a fixed locationidentifier 1000 or network connection element 900, the object identifier800 may be identified as being within specific room, office or area.

An electronic device 1101 is provided to host the location resolver1100. According to this embodiment the location resolver 1100 is in theform of software operating on the electronic device 1101. Examples ofelectronic devices 1101 l include computers, processors or other devicescapable of implementing the functionality of the location resolver 1100.

As shown by way of example, a location determining module 14, accordingto an embodiment of the invention, is illustrated, by way of example, asincluding one of the fixed location identifiers 1000, the network 400,the electronic device 1101, the location resolver 1100, the database1150 and topology database 1152.

An example of a location system in use in a health care institutionsetting is illustrated in FIG. 13. As shown by way of example in FIG.13, a network 400 is provided to allow for communication among multiplenetwork connection elements 900. A location resolver 1100 is alsoprovided in communication is also provided in communication with thenetwork 400. It is noted that the network is not limited to a wirednetwork, as the network may be a wireless network. A fixed locationidentifier 1000 is illustrated and is in communication with the networkconnection elements 900. Various object identifiers 800 are illustratedas a fixed to various pieces of equipment within the health careinstitution setting. The object identifiers 800 may be in communicationwith one or more of each of the network connection elements 900 and thefixed location identifier 1000.

As illustrated in FIG. 14, a network interface 992, 1120 is shown by wayof example according to an embodiment of the invention. The networkinterface 992, 1120 may be used in one or more of the network connectionelements 900 and/or location resolver 1100 or other components adaptedfor communication with a network. A network interface 992, 1120 isadapted to be directly coupled to a network. The network interface 992,1120 may be configured with one or more of the appropriateconfigurations for the corresponding networks. For example, it isillustrated by way of example in FIG. 14, the network interface 992,1120 may be configured to be directly to an Ethernet network by way ofEthernet circuitry 994. According to a further embodiment, the networkinterface 992, 1120 may be coupled to a telephone system to a modem 996.According to another embodiment of the invention, the network interface992, 1120 may be provided with one or more of a cable televisionmodulator 998 to allow communication with a cable T.V. network, a UTPnetwork card 1122, to allow communication with a UTP network, or auniversal serial bus (USB) card 1124 and/or a medical telemetrytransmitter 1126 for communication with a medical telemetry network.

The present invention has been described by way of example, andmodifications and variations of the described embodiments will suggestthemselves to skilled artisans in this field without departing from thespirit of the invention. Aspects and characteristics of theabove-described embodiments may be used in combination. The describedembodiments are merely illustrative and should not be consideredrestrictive in any way. The scope of the invention is to be measured bythe appended claims, rather than the preceding description, and allvariations and equivalents that fall within the range of the claims areintended to be embraced therein.

1. A method for determining location of an object, comprising the stepsof: determining a potential target area; and estimating a targetlocation within the potential target area.
 2. The method of claim 1,wherein the step of determining a potential target area comprises thesteps of: identifying receivers that received a signal from atransmitter; generating one or more line segments connecting theidentified receivers; determining zones around identified receivers;generating lines through intersections of zones and the one ore morelines; and designating the area defined by secants as the potentialtarget area.
 3. The method of claim 2, wherein the step of generatinglines comprises generating secants through the intersections between theline segments and the zones for each zone.
 4. The method of claim 2,wherein the step of generating lines comprises generating tangents atthe intersections between the line segments and the zones for each zone.5. The method of claim 2, wherein said zones are rings.
 6. The method ofclaim 2, wherein said zone is defined as a sphere.
 7. The method ofclaim 2, wherein a size of said zones is scalable
 8. The method ofclaims 2, wherein said zones are determined using received signalstrength indication.
 9. The method of claims 1, wherein said zones aredetermined using time of arrival of one or more signals.
 10. The methodof claim 1, wherein the step of estimating a target location within thepotential target area comprises finding the center of the potentialtarget area.
 11. The method of claim 1, wherein the step of determininga potential target area comprises the steps of: for a receiver,estimating a first zone within which a first transmitter is located; forremaining receivers that can detect a given transmitter, each estimatinga second zone within which a first transmitter is located; anddetermining if there are overlaps in any of the zones.
 12. A method fordetermining location of an object, comprising the steps of: for areceiver, estimating a first zone within which a first transmitter islocated; for remaining receivers that can detect a given transmitter,each estimating a second zone within which a first transmitter islocated; and determining if there are overlaps in any of the zones. 13.The method of claim 12, wherein said estimation steps yield a vector(Zn-m)₁, (Zn-m)₂, (Zn-m)₃ . . . (Zn-m)_(P) where P is the number ofreceivers that can hear said first transmitter.
 14. The method of claim12, wherein said zone is defined as a ring.
 15. The method of claim 12,wherein said receiver has a plurality of zones each defined as a ring.16. The method of claim 12, wherein said plurality of zones are definedas concentric rings.
 17. The method of claim 12, wherein said zone isdefined as a sphere.
 18. The method of claim 12, wherein said receiverhas a plurality of zones each defined as a sphere.
 19. The method ofclaim 12, wherein said plurality of zones are defined as concentricspheres.
 20. The method of claim 12, wherein a size of said zones isscalable.
 21. The method of claims 12, wherein said estimation steps usereceived signal strength indication to determine location.
 22. Themethod of claims 12, wherein said estimation steps use time of arrivalof one or more signals to determine location.
 23. A method fordetermining location of an object, comprising the steps of: identifyingreceivers that received a signal from a transmitter; generating one ormore lines segments connecting the identified receivers; determiningzones around the identified receivers; generating lines throughintersections of zones and the one ore more line segments; designatingthe area defined by the lines as the potential target area; anddetermining center of potential target area.
 24. The method of claim 23,wherein the step of generating lines comprises generating secantsthrough the intersections between the line segments and the zones foreach zone.
 25. The method of claim 23, wherein the step of generatinglines comprises generating tangents at the intersections between theline segments and the zones for each zone.
 26. The method of claim 23,wherein said zone is defined as a ring.
 27. The method of claim 23,wherein said zone is defined as a sphere.
 28. The method of claim 23,wherein a size of said zones is scalable.
 29. The method of claims 23,wherein said zones are determined using received signal strengthindication.
 30. The method of claims 23, wherein said zones aredetermined using time of arrival of one or more signals.
 31. In acomputing device, a method for determining location of an object,comprising the steps of: for a receiver, estimating a first zone withinwhich a first transmitter is located; for remaining receivers that canreceive a given transmitter, each estimating a second zone within whicha first transmitter is located; and determining if there are overlaps inany of the zones.
 32. In a computing device, a method for determininglocation of an object, comprising the steps of: identifying receiversthat received a signal from a transmitter; generating one or more linesegments connecting the identified receivers; determining zones aroundthe identified receivers; generating lines through intersections ofzones and the one ore more line segments; designating the area definedby lines as the potential target area; and determining the center of thepotential target area.
 33. A computer program product holdinginstructions executable in a computer for determining location of anobject, the instructions comprising the steps of: for a receiver,estimating a first zone within which a first transmitter is located; forremaining receivers that can receive a given transmitter, eachestimating a second zone within which a first transmitter is located;and determining if there are overlaps in any of the zones.
 34. Acomputer program product holding instructions executable in a computerfor determining location of an object, the instructions comprising thesteps of: identifying receivers that received a signal from atransmitter; generating one or more line segments connecting theidentified receivers; determining zones around the identified receivers;generating lines through intersections of zones and the one ore moreline segments; designating the area defined by lines as the potentialtarget area; and determining the center of the potential target area.35. In a location system comprising at least one transmitter and atleast two receivers, a method comprising: determining which receiverscan receive a signal from the transmitter; estimating the zones of thereceivers the transmitter is in; determining if there are overlaps inany of the zones.
 36. The method of claim 35 further comprising the stepof determining the area of overlap between zones.
 37. The method ofclaim 35 further comprising the step of determining the volume ofoverlap between zones.
 38. A location system for determining location ofan object, comprising a location determination module for determining apotential target area encompassing the object, and estimating thelocation of the object within the potential target area.
 39. Thelocation system of claim 38, wherein the location determining modulecomprises a receiver.
 40. The location system of claim 38, wherein thelocation determining module comprises a network.
 41. The location systemof claim 38, wherein the location determining module comprises a networkconnection element.
 42. The location system of claim 38, wherein thelocation determining module comprises a location resolver.